Method of tanning hide



United States Patent METHOD OF TANNING HIDE Richard W. Alsgaard and John W. Gilkey, Midland,

Mich., assignors to Dow Corning Corporation, Midland, Mich., a corporation of Michigan No Drawing. Filed Dec. 15, 1958, Ser. No. 780,229

2 Claims. (Cl. 8-94.33)

. dioxide. These pigments cover up the color of the leather.

Ordinarily such white leather functions satisfactorily for most applications. However, it has been impossible leather deteriorates quite rapidly. Consequently, such conditions should obviously be avoided. Any alkaline material can be used to regulate the pH. Examples of suitable materials include alkali metal carbonates, alkaline earth metal oxides and hydroxides, alkali metal salts of carboxylic acids and ammonia.

The amount of organosilicon compound employed should be at least 10% of the dry weight of the hide Larger amounts relative to the hide can be employed if desired. There is no critical upper limit to the amount of the organosilicon compound although for practical purposes large excesses should be avoided due to the ex-. pense of organosilicon compounds.

The temperature at which the operation of this inven tion is carried out is not critical. However, satisfactory results are obtained at room temperature and ordinarily 4 there is no reason to vary therefrom.

to render the presently available commercial white leather water repellent with silicones. Inasmuch as silicone water repellents are highly desirable for use on leather, the inability to water repel present commercial White leathers has been a disadvantage. For example, nurses shoes are often in contact with water borne materials which are deleterious to leather. It would be highly desirable, therefore, it silicone water repellents could be satisfactorily applied to such shoes. However, to date, this has not been feasible.

It is the object of this invention to provide a novel procedure for tanning leather. Another object is to provide a white leather which can be made water repellent with commercial silicone water repellents. Other objects and advantages will be apparent from the following description.

This invention relates to a method of preparing leather which comprises contacting hide with an aqueous dispersion of an organosilicon compound of the formula CH3 (ROMSKCHQDO CHECK-43115 in which R is an aliphatic hydrocarbon radical of less than 4 C atoms and n is an integer of from 2 to 3 inclusive, said dispersion having a pH of at least 9 until the hide is suitably tanned, the organosilicon compound being present in amount of at least 10% of the dry weight of the hide.

In carrying out the process of this invention the hide can be contacted with the aqueous dispersion of the organosilicon compound in any desired manner. The aqueous dispersion can be either in the form of a solution of the organosilicon compound or an emulsion thereof. In general, the preferred method is to immerse the hide in the aqueous dispersion and agitate the mixture until the hide is suitably tanned. The time of tanning is not critical and, in general, satisfactory results are obtained after the hide has been in contact with the dispersion for from 10 to 24 hours. It should be understood, of course, that shorter or longer times may be employed if desired.

In order for the process of this invention to operate successfully the pH of the aqueous dispersion should be at least 9. There is no critical upper limit to the pH eacept that under extremely strong alkaline conditions For the purpose of this invention R can be any aliphatic hydrocarbon radical of less than -4 carbon atoms such as methyl, ethyl, propyl, isopropyl and allyl. The organosilicon compounds employed herein are best prepared by reacting the dialkoxysilanes of the formula on, nonsin with vinyl and allyl glycidyl ethers in the presence of a platinum catalyst (i.e. chloroplatinic acid) at to C. Under these conditions the addition of the-SiH to the vinyl or allyl group in the ether takes place to produceflthe compounds of this invention in which n is 2 or 3 respectively Those compounds in which R is unsaturated are best prepared by an ester interchange between CH3 (CHsO)2Si(C 2) no CHrCH-CH:

and an unsaturated alcohol such as allyl alcohol. During the interchange methanol is given ofi.

After the hides of this invention have been tanned the resulting leather can be subsequently treated by any of the conventional processes which are employed to render leather suitable for fabrication. That is, the leather can be fat liquored with any of the conventional fat liquoring agents and it can be finished with any of the conventional finishing agents. Also, if desired, the leather can be rendered water repellent with any of the conventional leather water repelling agents, preferably with silicone water repellents.

The process of this invention can be carried out with any of the commonly employed animal hides such as horsehide, pigskin, sheepskin, goatskin, cowhide and the like.

The following examples are illustrative only and should not be construed as limiting the invention which is properly delineated in the appended claims.

Example 1 A piece of limed, bated cowhide weighing 2744 g. (dry weight) was placed in 10 gallons of an aqueous solution having a .2 mol concentration of Na CO and containing 10% by weight Na SO based on the weight of the solution. The solution had a pH of 11. The hide was agitated in the solution at room temperature for 2 hours and then 880 g. of

was added and the agitation continued for 24 hours after which time the leather was removed and washed. The leather so produced had the following properties. The color was white, the shrinkage temperature was 82 C. and the leather was 96% undigested after the papain digestation test. The latter was run in accordance with Patented Feb. 7, 1961 a ees;

'(sold under the designation I OIZW), said emulsion having a concentration of 6.5% oil. A second portion (2) of-the leather was fat1liquored with another emulsion of l012W,'said emulsion having a; concentration of 9% oil. A third portion (3) was "felt liquored with an aqueous emulsion of 4% by weight of a siloxane composed'of a v mixture of equal" parts; by weight of a dimth-ylpolw siloxane fluid and a methylpolysiloxane resin.. The resin was composed 'o'f'a copolymer of trimethylsiloxy groups and SiO' units. In each case the resulting leather was flexible ahd'pliable' and suitable for use in the fabrication of articles.

Fat' liquoi-ed leather ('1) shown above was cut into 8 samples and each'was immersed in a 15% solution of the siloxane water repellent shown infUiS. Patent Re. 23,879. The samples were tested for water penetration inaccordance with the flex test shown in said patent. The average number of flexes before water penetrated was 6172. This compares with the commercially acceptable water penetration of 4000 flexes for. leather treated with this silicone water repellent. This'test shows that the'white leather L of this invention can be satisfactorily water repelled with 1 v-corral-ne'reially; available silicone" water repellents.

4 Example 2.,

Equivalent results are obtained when the following organosilanes are substituted in the process of Example 1:

That which is claimedis: r

1. A method oft-preparing leather which comprises contacting hide with anaqueb'us dispersion of an organosilicon compound of the formula in which R i an a iphe chy roca bou.radiq otle sth 41C atoms and n is an int er f fr m to 3 i cl si e. a a, pH f at least 9 unti i h d u t bly vta ed, the o ga osilicon c mpound b in Pre en in amou t o t least 1.0 of the dry w ight of he hide.

Z. A method in accordance with claim I in which the organosilicon compound is No references cited.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,970,881 February 7, 1961 Richard W. Alsgaard et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as "corrected below.

Column 1, line 22, for "bleeding" read bleaching Signed and sealed this 31st day of October 1961.

' (SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Commissioner of Patents Attesting Officer USCOM M-DC- 

1. A METHOD OF PREPARING LEATHER WHICH COMPRISES CONTACTING HIDE WITH AN AQUEOUS DISPERSION OF AN ORGANOSILICON COMPOUND OF THR FORMULA 